User blog comment:Gelsadra/New theory or nobody ever think of it?/@comment-26082987-20150207000145/@comment-6769189-20150210190631

It was written and released after DMC4 by one of the storywriters that was on the team, to my understanding, after he had left Capcom.(1 reason i don't believe its canon.)

There were  a lot of scenes that were fairly different than in the game(another reason I dont believe it is canon)

A later developer interview states that DMC4 Lady is 10 years older than 3. I can get that for you later, they had apparently changed their story because they had stated earlier that Dante was in his 40's. I can get some threads that more or less confirm that the "10 years older" interview was the last word of age/timeline.